The invention relates to the field of heat exchangers manufactured by assembling brazed plates.
Reboiler/condensers for air separation units have in general, for several decades, been produced from aluminum or aluminum alloy by means of plates brazed together. They may also be made of copper, nickel, stainless steel or any other brazeable metal. These exchangers generally consist of two or more circuits, defined by the configuration of the plates of which they are composed and of the possible separating elements of the plates such as heat-exchange fins that the exchanger may contain. The various fluid circulation circuits are connected to the rest of the plant via a system of pipes welded to the exchanger.
The material serving to form the braze is conventionally deposited by depositing a powder, wires or foils onto the regions of the exchanger to be brazed. The material may be deposited in this way either on the plates of the exchanger or on the heat-exchange fins. Given the number and length of the regions to be brazed, the operation of depositing the brazing material is very expensive and not very reliable. In the case of powders, the problem arises as to their distribution over the brazing region. When wires or foils are deposited, these may have undulations and pleats which make the effectiveness of the brazing random. Moreover, in general the materials used for the braze are often noble alloys, for example containing silver in a large amount. Since these alloys are very expensive, it would be beneficial to minimize as far as possible the amount of brazing alloy used, without correspondingly compromising the quality of the brazing.
The object of the invention is to provide manufacturers of plate heat exchangers with a method of assembly by brazing which is both less expensive and more reliable than the conventional assembly methods.